A rock crushing system generally breaks apart rock, stone or other material in a crushing gap between two elements. For example, a conical rock crusher is comprised of a head assembly including a crushing head which gyrates about a vertical axis within a stationary bowl attached to a main frame of the rock crusher. The crushing head is assembled with an eccentric mechanism that rotates to impart the gyrational motion of the crushing head which crushes rock, stone or other material in a crushing gap between the crushing head and the bowl. The eccentric mechanism can be driven by a variety of power drives such as an attached bevel gear, driven by a pinion and counter shaft assembly, and a number of mechanical power sources, such as electrical motors or combustion engines.
The exterior of the conical crushing head is covered with a protective or wear resistant mantle that engages the material which is being crushed, such as rock, stone, ore, minerals or other substances. The bowl which is mechanically fixed to the main frame is fitted with a bowl liner. The bowl liner and the bowl are stationary and spaced apart from the crushing head. The liner provides an opposing surface from the mantle for crushing the material. The material is crushed in the crushing gap between the mantle and the liner.
The gyrational motion of the crushing head with respect to the bowl crushes rock, stone, or other material within the crushing gap. Generally, the rock, stone or other material is fed into a top of the crushing gap and is crushed as it travels through the crushing gap and exits at a bottom of the crushing gap. The size of the crushing gap determines the maximum size of crushed material which exits the crushing gap.
Generally, the bowl is movably attached to the adjustment ring which is connected to the main frame. The size of the crushing gap can be adjusted by vertically moving the bowl with respect to the crushing head. As the bowl vertically moves with respect to the adjustment ring and main frame, the bowl and bowl liner move vertically with respect to the mantle. A conventional crusher, such as, an HP700™ conical rock crusher manufactured by Metso Minerals of Milwaukee, Wis. includes a bowl threaded to an adjustment ring which is fixed to the main frame by tramp release cylinders. The bowl and connecting adjustment cap is coupled to a gear which surrounds the adjustment cap.
A conventional adjustment mechanism comprised of a hydraulic motor rotates the bowl with respect to the adjustment ring via the gear. The hydraulic motor rotates the bowl with respect to the main frame so that the bowl is vertically raised or lowered, thereby adjusting the gap size.
In another conventional crusher, an MP1000™ conical rock crusher manufactured by Metso Minerals of Milwaukee, Wis. includes an adjustment mechanism having four hydraulic motors. The four hydraulic motors are necessary to move the large bowl associated with the MP1000™ crusher. The four motors rotate the bowl with respect to the main frame to adjust the gap size.
Generally, the bowl must be moved with respect to the head in at least two different situations. First, the bowl is rotated with respect to the head to remove it from the rock crusher for repair and maintenance. Removing the bowl from the annular ring attached to the main frame requires a significant amount of time (e.g., over one hour) as the bowl is threadably disengaged from the annular ring. Alternatively, the bowl can be moved to various gap size heights to allow access and inspection of components of the rock crusher. Maintenance may include operations in which the mantle, crushing head, bowl liner, or bowl are repaired or replaced. Alternatively, other equipment in the crusher can be repaired and replaced or lubricated during maintenance operations. Generally, the bowl is removed when the rock crusher is not operational.
Second, the bowl is moved with respect to the head to adjust the gap size. The gap size is adjusted to alter the size of crushed material exiting the rock crusher. For example, to create crushed material which is smaller, the gap size is decreased. In contrast, to create crushed material which is larger, the gap size is increased. Generally, adjustments of the gap size to create smaller or larger size crushed material require relatively fine positioning of the bowl with respect to the crushing head (e.g., a slow rotation of the bowl with respect to the main frame is necessary).
The gap size can be adjusted while the rock crusher is operating (adjustment under load) or while the rock crusher is non-operational (no load). Adjustments under load require larger amounts of torque than the amount of torque required to adjust the bowl or remove the bowl under no load. Accordingly, conventional gap adjustment mechanisms have required a high torque, slow speed motor.
Certain conventional rock crushers, such as, the MP1000™ rock crusher have utilized two hydraulic pumps to drive the four hydraulic motors. The two hydraulic pumps allow the power unit to drive the four motors at two different speeds. One pump is used for the gap adjustments (e.g., slow speed), both pumps are used for installation and removal of the bowl assembly (e.g., high speeds). However, the use of two hydraulic pumps adds to the cost and size of the power unit.
Thus, there is a need for a low cost, an efficient variable speed gap adjustment mechanism. Further still, there is a need for a variable speed adjustment mechanism which does not require two hydraulic pumps.